Saturday, July 31, 2010

Righthanded gesturing in apes hints at the origins of human language The origins of language have long been a mystery, but mounting evidence hints that our unique linguistic abilities could have evolved from gestural communication in our ancestors. Such gesturing may also explain why most people are righthanded. Researchers at the Yerkes National Primate Research Center recently ex amined captive chimpanzees and found that most of them predominantly used their right hand when communicating with one another—for example, when greeting another chimp by extending an arm. The animals did not show this hand preference for noncommunicative actions, such as wiping their noses. Such lateralized hand use suggests that chimpanzees have a system in their left brain hemisphere that is coupled to the production of communicative gestures, says study author William Hopkins. The same cerebral hemisphere is host to most language functions in humans, which hints that an ancestral gestural system could have been the precursor for language, he says. That notion is supported by previous studies that have shown anatomical asymmetries in chimpanzees’ brains in areas that are considered to be ho mologues of human language centers, such as Broca’s area, Hopkins says. “Chimps that gesture with their right hand typically have a larger left Broca’s area, and those that don’t show a [hand] bias typically don’t show any asymmetry in the brain,” he notes. The idea that language emerged from an ancestral gestural system located in the left brain hemisphere could explain why the vast majority of people are righthanded, Hopkins says. If gesturing was strongly selected for in human evolution, then the fact that most people are righthanded is a consequence of that. This hypothesis challenges the longheld view that the opposite scenario is true: that righthandedness emerged for motor skills such as tool use and that communication built on the developed asymmetry in the motor system later.

Friday, July 30, 2010

The 1992 tearjerker Lorenzo’s Oil told the true story of one family’s struggle to save their son from Xlinked adrenoleukodystrophy (ALD), a deadly degenerative brain disease. Unfortunately, over the ensuing years, the oil of the fi lm’s title, a dietary supplement, has not panned out as the cure many people hoped it would be. Now a paper in the November 2009 issue of Science suggests that the longsought cure may come from gene therapy—a famously hyped approach to treatment that tragically caused the death of a teenage experimental subject in 1999. Since then, however, researchers have continued to cautiously pursue gene therapy for certain disorders with known genetic origins. ALD, for instance, is caused by mutations in a gene called ABCD1, leading to unusually high levels of a type of fatty acid that damages the material insulating some neurons. It affects about one in 20,000 sixto eight year old boys, leading to death before adolescence. The main treatment is still bone marrow transplantation: a risky procedure that relies on finding a suitable donor, explains Patrick Aubourg, a neurologist at France’s INSERM research institute. Now Aubourg and his team have showed in a preliminary trial that gene therapy stopped ALD in two boys for whom they could not fi nd matching bone marrow donors. After fi shing stem cells from each individual’s own blood, the researchers inserted a normal version of the ABCD1 gene into some of the cells and transplanted them back into the kids. The results were promising: ALD progression halted within 14 to 16 months. A year later neither child had further brain damage or leukemia (a side effect in some past gene therapy trials). The researchers have now treated a third individual and are preparing for larger trials in Europe and the U.S.

Thursday, July 29, 2010

A video before bed or a recording played while asleep can enhance learning

Listen and LearnLearning by listening to information as we sleep has long been a mainstay of science fiction—and wishful thinking— but a new study suggests the idea may not be so farfetched. What we hear during deep sleep can strengthen memories of information learned while awake. Researchers at Northwestern University taught 12 subjects to associate 50 images with specifi c positions on a computer screen. When the subjects saw each image, they also heard a matching noise—for instance, on seeing a cat, they heard a meow. Then the subjects each took a 60 to 80minute nap. While they were in slowwave sleep (a deepsleep phase marked by slow electrical oscillations in the brain), the researchers played the noises that matched 25 of the images they had been studying. On waking, the subjects were asked to perform the same image matching task. They were much better at correctly placing the images for which they had heard the noise cues while they napped. The participants reported they had no idea sounds had been played during their naps, and when asked to guess which sound cues they heard, they were just as likely to pick the wrong ones as the right ones. “We were certainly surprised,” says coauthor Ken Paller, director of the Cognitive Neuroscience Program at Northwestern, explaining that he did not expect such strong results. Although previous research has suggested that sleep alone can help consolidate memories, this study is the first to show that sound cues can strengthen specific spatial memories. Paller and his colleagues will next explore how long these effects last and whether aural cues can strengthen other types of memories as well. Until then, go ahead and play those French tapes while you snooze—it couldn’t hurt

A Movie and a NapPractice makes perfect, but can simply watching help, too? Yes, if you sleep on it right away, reports a study from the Netherlands Institute for Neuroscience. Ysbrand Vander Werf and his colleagues tracked how well people learned to tap their fi ngers in a specifi c sequence—without any practice. Watching a video of the finger tapping task led to faster and more accurate fi rst attempts at the target sequence only when study participants slept within 12 hours of the video, before being tested. The finding not only points to a promising way to augment practicing when learning a new physical skill, it could also help people regain skills after injuries such as stroke.Source of Information : Scientific American Mind March-April 2010

Wednesday, July 28, 2010

SLEEP'S effect on fat is becoming clearer. Having too much or too little piles on the worst kind of fat. Kristen Hairston and colleagues at Wake Forest University in Winston-Salem, North Carolina, monitored 1100 African and Hispanic Americans for five years. Both groups are at a high risk of obesity-related disorders. People under 40 gained 1.8 kilograms more on average if they got less than 5 hours of sleep per night than if they slept for 6 or 7 hours. Those regularly sleeping for more than 8 hours gained 0.8 kilograms more than the medium sleep group. CAT scans revealed increases in visceral fat, which accumulates around the internal organs and is particularly dangerous to health.

Tuesday, July 27, 2010

COULD these lines etched into 60,000-year-old ostrich eggshells be the earliest signs of humans using graphic art to communicate? Until recently, the first consistent evidence of symbolic communication came from the geometric shapes that appear alongside rock art all over the world, which date to 40,000 years ago (New Scientist, 20 February, p 30). Older finds, like the 75,000-year-old engraved ochre chunks from the Blombos cave in South Africa, have mostly been one-offs and difficult to tell a part from meaningless doodles.

The engraved ostrich eggshells may change that. Since 1999, Pierre-jean Texier of the University of Bordeaux, France, and his colleagues have uncovered 270 fragments of shell at the DiepkloofRock Shelter in the Western Cape, South Africa.

They show the same symbols are used over and over again, and the team say there are signs that the symbols evolved over 5000 years. This long-term repetition is a hallmark of symbolic communication and a sign of modern human thinking, say the team (Proceedings of the National Academy of Sciences, DOl: 1O.1073/pnas.0913047107). The eggshells were probably used as containers, and the markings may have indicated either the shells' contents or their owner. Texier points out that until recently, bushmen in the region carved geometric motifs on ostrich eggshells as a mark of ownership. If the symbols do signify ownership, it could have implications for the evolution of human cognition. lain Davidson, an Australian rock art specialist at the University of New England in Armidale, New South Wales, has suggested that marking ownership must have come after humans became self-aware. The eggshells could help to illuminate when this happened in this part of the world, he says.

Written language may have evolved more than once in human history. "judging from what we know about the evolution of art all over the world, there may have been many traditions that were born, lasted for some time and then vanished," says jean Clottes, former director of research at the Chauvet caves in southern France. "This may be one of them, most probably not the first and certainly not the last."

Monday, July 26, 2010

A CHEMICAL produced during sex and l inked to addiction has been visualised in a scanner as it washes across rats' brains. The feat means that functional magnetic resonance imaging (fMRI), a workhorse of neuroscience, can now be used to observe the flow of brain chemicals, not just oxygen - rich blood. By pin pointing increases in blood oxygenation in the brain in response to different events - a sign that specific groups of neurons are active - fMRI is responsible for some of the hottest findings about the brain . Now Alan jasan off at the Massachusetts Institute of Technology and colleagues have extended its power.

His team repeatedly mutated a magnetic, iron-containing enzyme that "lights up" i n fMRI readings. With each mutation, the researchers tested its tendency to bind to dopamine, a learning and reward chemical in the brain involved in sex and addictive behaviors. Mutations that increased this tendency were combined, resulting in a molecule that was both magnetic and strongly attracted to dopamine.

The team injected the molecule into the brains of rats, in a region laden with dopamine-producing celis. When given a chemical that triggers dopamine release, that area "lit up" under fMRI (Nature Biotechnology, 001: 1O.103B/nbt.1609). Because the molecule must be injected into the brain, this kind of chemical- based fMRI won't be applied to humans anytime soon, says jasan off. b u t it could be used to probe addiction and disease using animals. His lab is now using the enzyme to view how dopamine-sensitive neurons across animal brains react when the chemical is produced in a specific region. The technique could also be used to probe dopamine's role in diseases such as Huntington's. The magnetic enzyme can in theory b e "evolved" t o b i n d t o other brain chemicals. Ewen Callaway

Sunday, July 25, 2010

BOOZE that has been treated so that you sober up faster afterwards may sound like a drinker's dream. But could end up being their down fall if it encourages heavy drinkers to consume even more alcohol. Kwang-il Kwon and his colleagues at Chungnam National University in Daejeon, South Korea, gave 30 men and 19 women 360 milliliters of a drink containing 19.5 per cent alcohol by volume, about the strength of fortified wine or sake. The drinks also contained 8, 20 or 25 parts per million of dissolved oxygen, which is known to play a role in alcohol breakdown by the body. It took about 5 hours for the blood alcohol levels of volunteers to reach zero. But Kwon's team found that on average, those whose drinks contained 20 or 25 ppm of oxygen went to zero 23 minutes and 27 minutes faster respectively than those who had the lowest-oxygen drinks (Alcoholism: Clinical &­Experimental Research, DOl: 10.lll1/j.1530-0277.2010.01155.x).

The researchers suggest that enriching alcoholic drinks with oxygen might "allow individuals to become sober faster". 'The reduced time to a lower blood-alcohol concentration may reduce alcohol• related accidents," they write. A spokeswoman for the British Medical Association was unimpressed. "We would n't want a situation where people drank more simply because they would recover quicker."

Saturday, July 24, 2010

IT WORKS for crops. Now a common organic pesticide could cure hundreds of millions of people of intestinal worms, if cash can be found for trials. More than 1 billion people, almost all of them living below the World Bank's poverty line, are infected with nematodes. While the worms don't usually kill, they stunt growth, cause anaemia and impair cognitive development. All this helps to "trap the 'bottom billion' in poverty", says Peter Hotez, a specialist in tropical diseases at George Washington University in Washington DC. The current treatment doesn't work well on all types of worms – and resistance is emerging. Now Raffi Aroian at the University of California, San Diego, and colleagues have shown that the protein CrySB, produced by the bacterium Bacillus thuringiensis and used as a crop pesticide, could act as an effective drug. An oral dose cleared around 70 per cent ofthe worms from infected mice (PLoS Neglected Tropical Diseases, DOl: 10.1371/journal.pntd.oooo614.t002). CrySB is about three times as effective as tribendimidin, the leading drug in development. A big obstacle is a dearth of funding for human trials, says Aroian.

Friday, July 23, 2010

IF YOU'RE one of those committed atheists in the Richard Dawkins mould who dreams of ridding the world of religious mumbo-jumbo, prepare yourself for a disappointment: there is no good evidence that education leads to secularisation. In fact, the more we learn about the "god instinct" and the refusal of religion to fade away under the onslaught of progress, the more the non-religious mindset looks like the odd man out. That is why anthropologists, psychologists and social scientists are now putting irreligion under the microscope in the same way they once did with religious belief. The aim is not to discredit atheism but to understand how so many people can override a way of thinking that seems to come so naturally. For that reason, atheists should welcome the new scrutiny. Atheism still has a great deal to commend it, not least that it doesn't need supernatural beings to make sense of the world. Let's hope the study of atheism leads to new insights into how to challenge such irrationality.

Thursday, July 22, 2010

Coercive interrogation is ineffective and damaging, We need a more effective and humane approach

HOWLS of outrage greeted US Attorney General Eric Holder's decision to try Khalid Sheikh Mohammed - who claims to have masterminded the 9/11 attacks on New York and Washington - in a civilian court rather than before a military tribunal. The protesters' wish to see Mohammed treated as an enemy combatant is perhaps understandable, but in fact dealing with suspected terrorists in this way has a poor track record.

Since 2001, US military commissions have convicted just three detainees of perpetrating terrorist acts. Civilian courts have secured around 150 convictions. Why the difference?

The "enhanced interrogation" techniques sanctioned by the Bush administration after 9/n have surely not helped: as we report this week, they are both inhumane and ineffective. Practices such as sleep deprivation, isolation and forcing prisoners to maintain stress positions may fall outside the legal definition of torture but their impact can be just as damaging. And as with "proper" torture, they often fail to yield any information at all, or elicit worthless statements by causing detainees to lose touch with reality.

President Barack Obama has tried to draw a line under all this with the establishment ofa team of elite interrogators, the H ighValue Detainee Interrogation Group, that will only use "scientifically proven", humane techniques. But where these will come from is hard to know, as the research has simply not been done.

There is, however, a promising alternative to coercion, and though it may seem at first sight like a feeble strategy for dealing with people thought to be bent on mass murder, it has much to recommend it. It is simple persuasion, something that has been the subject of intense academic interest for decades, and that modern consumer societies have become very good at.

Here is a field in which science really can point to effective techniques for extracting useful information. We know, for example, that successful persuasion rests on the reputation of the person doing the persuading. This may help explain the civilian justice system's greater success at bringing terrorists to book: they have a much better reputation for fair dealing than the military tribunals system.

Commenting on the announcement that the alleged Christmas day bomber Umar Farouk Abdulmutallab - who is to be tried by the civilian courts – is cooperating with the FBI, Holder said: "You are much more likely to get people to cooperate with us if their belief is that we are acting in a way that is consistent with American values."

If the security services want to improve their reputation there is a proven way: reputation requires trust, and trust rests on openness. For that reason, the workings of Obama's new interrogation group must be more transparent than the shadowy world ofGuantanamo Bay. That would begin to repair the damage done to America's reputation. It might also deliver the result that is surely to be desired: better intelligence, more terrorists behind bars, and less torture .

Wednesday, July 21, 2010

Seeing that your tongue detects only a few different flavor types, it seems odd that we can distinguish between a roast beef and a rutabaga (never mind between different vintages of Zinfandel).

A good part of this disparity is thanks to your nose’s chemical-sensing abilities. As you eat, volatile chemicals stream off the food in your mouth, rise through the back of your throat, enter your nasal cavity, and arrive at the same odor detectors you saw on page 124. These detectors work in conjunction with the primary tasting ability of your tongue to generate endless variations of flavor. In fact, some studies suggest that the tongue is a bit player in the sensation of taste, and that 80 percent of taste takes place in your nasal cavity.

For many years, food scientists thought the interplay between tongue and nose was the whole story behind taste. However, more recent research shows that taste involves an impossibly complex mix of factors:

• Texture. The feel of food as it gives way to your teeth and mixes in your mouth changes how you feel about it. For example, study participants rank a thick cheese sauce as tasting cheesier, even if extra flour is the only difference. And if you doubt the power of texture, try putting some hot, crispy french fries in a plastic bag for a few minutes, then see if you feel the same way about the identically flavored soggy sticks that emerge. Or compare the sweetness of a fizzy drink with an identical one that went flat half an hour ago.

• Temperature. Hot food is tastier because its volatile chemicals are more likely to drift to your nasal cavity and trigger different odor receptors. However, even without this factor, the temperature of food influences your overall experience. Think, for example, how soup warms your stomach, and why you’ll never mistake a spoonful of ice cream for butter or yogurt.

• Touch (or pain). Some sensations that happen on the tongue have nothing to do with your taste buds. Examples include the tingle of alcohol, the coolness of mint, and the sear of hot spices. These compounds mess with the other nerve endings in your tongue, and some, like hot chile peppers, actually cause pain. (Chile-pepper survival advice: Because the active ingredient is an oil, water does little to wash it away. The fat in whole milk or the alcolhol in beer dissolve it more easily. By comparison, the singe of mustard and wasabi is shorter-lived because most of its kick comes from the odor receptors in the nasal cavity.)

• Appearance. Cooks are taught that the first bite is with the eye, and there’s a solid body of science that suggests they’re right. Just changing the color of foods causes people to imagine different tastes. For example, study participants will stubbornly describe orange-flavored, yellow-colored Jell-O as tasting like pineapples. A similar effect has been noticed with white wine that’s dyed red.

• Combinations. When you pair different flavors, the result is more than the sum of its parts. For example, tasters may claim a strawberry tastes more strongly like strawberries when it’s diluted with water and sweetened with sugar.

• Expectations. There’s a reason that food tastes better when you dine at a fine restaurant. The framework of assumptions and expectations you have when you approach a meal conditions your brain to perceive it in a certain way. Current emotions and past experiences are particularly powerful: from fond childhood memories of Grandma’s apple pie to the time you projectile vomited mint-chocolate ice cream on the Tilt-A-Whirl.

In short, your perception of flavor relies on all your senses, your memories, and your current state of mind. It’s one of your body’s great surprises: A simple sense that seems to involve little more than a few bumps on your tongue just might be your body’s strangest door of perception.

Tuesday, July 20, 2010

You eat a varied diet and plenty of vegetables. Your best friend subsists on diet soda and cheese pizza. Is she hopelessly spoiled, or is her perception of taste just wired differently? Modern science might have the answer.

In recent years, scientists have begun discussing supertasters—individuals who experience taste more strongly than others, and who are more likely to be picky eaters. Supertasters are particularly sensitive to bitter flavors (which they often shun). Research suggests that in the U.S., roughly 35 percent of women and 15 percent of men are supertasters.

If all this sounds made up, you’ll be surprised to hear that a scientific test can sift out supertasters. The test is remarkably simple. Participants taste a solution that includes a chemical like propylthiouracil. Many people find this taste mildly unpleasant, but supertasters find it stomach-churningly awful. Still other people (called, rather sadly, nontasters) say the mystery chemical has no taste at all.

You can test your own tasting abilities using an at-home kit, like the kind sold on http://supertastertest.com. Or you can try the crude experiment discussed next, which uses dye to help you estimate the number of taste buds on your tongue. (The current thinking is that supertasters have a heavier concentration of taste buds on their tongues, but this is probably not the only reason for supertasting.)

Here’s how to perform the test:1. Gather up your supplies: some blue food coloring, a piece of paper with a 7-millimeter (about a quarter-inch) hole punched through it, and a magnifying glass.

2. Using a cotton swab, rub some of the food coloring onto the tip of your tongue. Your tongue will absorb the dye, but the tiny papillae will stay pink. This is where your taste buds are.

3. Put the piece of paper over the front part of your tongue.

4. Using the magnifying glass, look at the hole. Now count how many pink dots you see within the hole. A score of fewer than 15 suggests you’re a nontaster. A count of from 15 to 35 ranks you as normal, while anything greater suggests supertasting abilities.

Supertasters don’t necessarily have a better sense of taste than normal people. It all depends on your perspective. Yes, supertasters have a stronger reaction to certain tastes, but there’s still much to be said for a cultured palate—in other words, a broad love of food honed through years of comparative tasting.

Monday, July 19, 2010

Your tongue has a limited variety of taste receptors because sugar, salt, and fat were the flavors most important for human survival over the last few million years of evolution. Your tongue craves sweetness because it signals ripe fruit. You yearn for salt because it’s an essential compound for basic body function. You long for fat because it’s an extremely dense source of dietary energy. On the other side of things, sourness can alert you to spoiled food, and bitterness can warn you about poisonous substances.

Our sense of taste is a great tool when we need to select nutritious, non-toxic foods from a natural environment. However, its effects aren’t as positive when we use it to guide food creation—for example, when we engineer heavily refined foods like candy-coated breakfast cereal. In this situation, our natural preference for sweet and salty runs rampant, producing foods that are literally too much of a good thing. These foods still tastegood on our tongues, but over time they can throw our bodies seriously off kilter.

The good news is that learned associations can gradually trump our built-in drive for sugar, salt, and fat. After all, many highly prized tastes involve a complex assortment of flavors along with the sour or bitter notes we normally avoid. For example, chocolate, coffee, beer, citrus peel, and greens like escarole all have strong bitter notes that we enjoy when matched with other flavors. There’s a good evolutionary reason for this flexibility— generations ago, humans who could discover new, untapped sources of food had a huge survival advantage.

This is particularly significant if you’re a parent and you want to expand your kid’s taste universe beyond chicken nuggets and plain pasta. The best advice is to present new foods, several times, with no conditions. Avoid resorting to bribery, bargaining, or threats, all of which place a taste “value” on food. (For example, using chocolate as a reward for eating spinach teaches that chocolate is desirable and spinach is not.) While you’re unlikely to find a child who prefers rapini to peanut butter, in time we can all learn to love a wide range of flavors.

Sunday, July 18, 2010

Your brain quickly adapts to new smells. What smells pungently strong on the first sniff becomes almost undetectable a few minutes later. This phenomenon, called odor fatigue, is similar to the way the hum of an air conditioner fades into background noise, but odor fatigue is more powerful. That’s because once you lose track of a smell, you can’t will yourself to get it back—at least not without first leaving the room and smelling something else.

Odor fatigue makes perfect sense when you consider the evolutionary role of smell. Your body is more interested in using smell to detect things than it is in keeping track of them. Once you notice a smell and decide how you want to react, it’s time to move on so you can detect the next potentially important odor.

Now that you understand how odor fatigue lets you ignore prolonged smells, there are a few practical bits of advice to consider:

• To determine if an object or room in your house smells, start by walking out the door and giving your nose a break. Then step back inside and pay attention.

• To determine if you have body-odor issues, you’ll need the help of a friend who can sniff you out.

• Just because you can ignore a smell doesn’t mean you should. Irritants and even toxins, ranging from cleaning products to cigarette smoke, are easy to ignore if you live with them, but they might not be so easy on your lungs. If in doubt, open a window and get some fresh air.

Saturday, July 17, 2010

An average young person can hear a staggering range of sound vibrations from 20 Hz to 20,000 Hz. (A Hertz is one vibration per second. So 20,000 Hz is a vibration that happens 20,000 times each second.) Of course, you won’t hear all pitches equally well. The middle-range pitches are the easiest to detect. A sound that’s similarly loud but extremely high-pitched will seem much quieter to your ear. You’ll notice a similar fall-off as you descend to the rumbles of low-frequency sound, although you’ll begin to feel them reverberate through your body.

As you age, the upper range of your hearing shrinks. For example, the hearing of a normal, middle-aged adult tops out at a significantly lower (but still impressive) 14,000 Hz. This change has been used to some effect by clever people on both sides of the age divide. For example, one company sells a sound device called the Mosquito Ultrasonic Teen Repellent (www.noloitering.ca). It emits an annoying sound that only young people can hear. Put it in a place where you don’t want crowds of teenagers to loiter—say, a mall parking lot—and it’s sure to drive them away. A similarly inventive product is the Teen Buzz ringtone (www.teenbuzz.org). Teenagers use it to announce text messages on their cell phones without alerting teachers and other authority figures in the over-30 crowd.

To test your own hearing and find the highest frequency you can detect, try an online hearing test (like the one on www.phys.unsw.edu.au/jw/hearing.html). Of course, these tests depend on some factors you can’t control, such as the quality of your speakers and the noise your computer makes, so they’re not perfectly accurate.

Friday, July 16, 2010

Black-and-white vision is a one-dimensional affair. A given shade can get blacker or whiter, but that’s it. Color vision (by which we mean human color vision) has three variables. You can modify any color by changing the amount of red, green, or blue in it. This mix of colors triggers different cones in your eye, creating the perceptual experience of seeing a single, specific shade.

But some animals aren’t limited to three types of cones. Consider birds, whose eyes have a number of advantages over yours. Their eyes are stacked with more cone, and these cones are arranged in larger patches (or in multiple patches) and packed more closely together. This arrangement gives some birds spectacularly sharp vision over long distances. But the most remarkable feature of birds’ eyes is how their cones work. Unlike your eyes, which have three types of cones, birds’ eyes have four or five distinct types of cones.

So what does this mean? Imagine meeting a pigeon and traveling with it to the countryside. Your eyes will collect the same reflected light as the pigeon’s eyes. You’ll see the same scenery. But the pigeon will perceive that light differently. Its eyes will break the rolling hills into a mix of four primary colors, while you translate them to a measly combination of three. For the pigeon, the contrast of certain wavelengths of light will become more dramatic, allowing it to spot details that your eyes miss. The difference is a little like leaping from black-and-white to color vision. Ultimately—and there’s no way around this—the pigeon will get a subtler, more nuanced view of the outside world.

So the next time an interior decorator scolds you for mistaking pistachio green for chartreuse, remind yourself that in the eyes of a pigeon, we’re all color-blind.

Thursday, July 15, 2010

Your retina is packed with light-sensing cells. But you may not realize that these light detectors come in two flavors:

• Rods. These are the most numerous light-sensing cells in your eyes. They’re extremely efficient at collecting light and continue working even in near-darkness. For this reason, your rods power your night vision. However, rods don’t distinguish between different colors.

• Cones. These cells are less sensitive than rods (meaning they need more light to do their work), but they’re able to perceive fine detail and color. Your eyes have three types of cones, which give you the ability to perceive three primary colors (red, green, and blue), provided there’s enough light for your cones to function.

Rods are spread throughout the sides of your eye. Cones are packed into a small region in the middle of your eye.

This combination of rods and cones gives your eye the best of both worlds—highly sensitive black-and-white vision you can use to creep around at night, and sharp color vision that catches more detail during the day. Although your brain switches effortlessly between the two, it takes 30 minutes of darkness to develop your best night vision. That’s because night vision requires chemical changes in your eye that make your rods more sensitive.

A short blast of ordinary light usually resets your vision from dark- to lightadjusted. However, dim red light doesn’t trigger this change because your dark-adjusted rods are naturally tuned to the blue end of the light spectrum, and they have a hard time picking up the color red. That’s why astronomical observatories and submarines use red light to illuminate dials and switches—it provides enough light for operators to see their instruments in a darkened environment, but it doesn’t disrupt their night vision.

Incidentally, most color-blind people have the same three types of cones as everyone else, but their cones don’t function normally. These people may have trouble discriminating between certain shades of color, but the effect is usually minor. Often, it goes unnoticed until they try a color-vision test (like the spot-the-number test at http://en.wikipedia.org/wiki/Ishihara_color_test). However, people with rarer, more serious forms of color-blindness may have only two functioning types of cones. They may be unable to distinguish purple from blue or red from yellow, except by the slight changes in brightness of the hues, not by the colors themselves.

Wednesday, July 14, 2010

Our eyes have a clear and obvious design flaw—they often fail to focus properly. This is a far greater problem than the eye’s other quirks, such as its blind spot and its inability to see certain colors. So why should such an elegant, intricate organ have such a glaring hitch?

Although there’s no definitive answer, many experts now believe that the problem has something to do with modern life. In the distant past, our ancestors spent most of their time wandering the savanna and staring into the distance. In today’s world, we spend far more time on near work—close-up activities like reading, writing, and drawing. During childhood, these activities may gradually reorient the eye from its natural state of mild farsightedness to the far more common condition of adult nearsightedness. In fact, our vision may have worked far better in the era before the invention of corrective eyewear (which was developed relatively recently, in 13th-century Italy).

Although this is all somewhat speculative, it may eventually lead to a way to prevent eye trouble. For example, children might be able to perform far-vision exercises to counterbalance the overload of near work. But for now, there’s no solution other than glasses and contact lenses, and there’s no evidence to suggest that you can help your eyes by cutting down on modern activities in adulthood. So now that your vision is already screwy, it’s safe to keep reading, writing, watching television, and surfing the Web.

Tuesday, July 13, 2010

On a good day, earwax does its job, trapping foreign material and gradually moving up your ear canal to the opening of your ear. There, it dries up and eventually falls out, its job done.

But earwax isn’t always so accommodating. Many people have particularly hard or sticky earwax. It becomes trapped inside the ear canal and can eventually plug it up, causing pain and blocking sound. In fact, this problem can happen to anyone, because the consistency of earwax can change abruptly and without explanation.

So what should you do about earwax? Don’t start digging with a cotton swab. Contrary to what you might have heard, they are safe for removing earwax, but only if you limit your swabbing to the opening of your ear canal and resist the urge to plunge in. Deeper swabbing is likely to compact wax, turning a partial blockage into a complete one. It’s also dangerous, because it risks damaging the sensitive eardrum or scratching the earcanal skin, which can lead to a painful infection.

So what can you do? If you don’t have problem earwax, you don’t need to do anything— after all, the wax in your ear canal belongs there, and it will migrate out in its own good time. But if you’re prone to wax of the ear-clogging variety, a simple practice can help prevent blockages. Put two or three drops of mineral oil into each ear every day (using an eye dropper). Over a couple of weeks, this softens wax so that you can remove it with a gentle flush of water. If your ear is completely blocked, head to your family doctor, who can wash it out or scoop it out using special tools.

Monday, July 12, 2010

Weak back muscles just can’t support your spine and battle gravity for an entire day. If you want your spine to stay healthy and pain-free, your best bet is to strengthen your back muscles with regular exercise.

Ideally, you’ll fortify your back with aerobic exercise (walking, running, dancing, and so on) and regular strength-training. Core exercises like abdominal crunches are particularly helpful because they reinforce the back and abdominal muscles that stabilize and support your spine.

The single most useful exercise for strengthening your back and relieving back pain is surprisingly simple and remarkably portable. You can do it on the floor of your home gym, in the chair at your office desk, or against the wall at a cocktail party. Pregnant women can use it to alleviate the excruciating backaches caused by their still-in-progress bundle of joy (on the floor up to the fourth month, against a wall thereafter). It goes by many names, including the one used in this chapter: the pelvic tilt.

If you have a pre-existing back condition or chronic back pain, doing the wrong kind of exercise (or doing the right exercise in the wrong way) could aggravate the problem. If you’re in doubt, check with your doctor, and never perform a back exercise that causes any sort of pain.

Here’s how to do the pelvic tilt:1. Lie on your back with your knees bent and your hands resting at your sides. (Or stand so you put your whole body—heels, bottom, and shoulders—against a wall.)2. Tighten your abdominal muscles and squeeze your lower back down against the floor (or wall, or chair). Alternatively, you can rest your hand on the small of your back and push against that.

3. Hold the squeeze for five seconds, but don’t hold your breath.

4. Relax your muscles, then repeat this sequence 10 to 15 times.

You can find many of the core exercises cited in this chapter described online. To get started, you’ll find good collections of back exercises at www.mayoclinic.com/health/back-pain/LB00001_D and http://tinyurl.com/cyybg9. (To save yourself some typing, you can find this link on the Missing CD page at www.missingmanuals.com.)Source of Information : Oreilly - Your Body Missing Manual

Sunday, July 11, 2010

We’re not about to crawl between the sheets with you and prescribe stiff rules about how to position your sleeping body. However, if you already suffer from bouts of back pain (whether caused by long hours of office work, heavy lifting, or pregnancy), you might find that sleeping in your regular positions is about as comfortable as having a prickly pear in your pajama bottoms. In this situation, you can try two tricks. First, if you’re a back sleeper, place a pillow under your knees. This takes the strain off your lower back. (If you want to adopt this position permanently, look for a wedgeshaped specialty pillow at a pharmacy or health store.) Second, if you sleep on your side, put a pillow between your knees. Again, this helps keep your spine in the straight, neutral alignment it likes best.

If you’re still not getting any relief for a sore back, consider the pelvic-tilt exercise. Not only can it relieve back pain, but it doesn’t require you to climb out of bed.

Saturday, July 10, 2010

One of the easiest ways to injure your back is through careless lifting. A proper lifting technique looks a bit like the squat exercise. Like the squat, it involves crouching down and using the strong muscles in your legs to do the brunt of the lifting, minimizing the stress you put on your back and reducing the amount you bend your spine. A little preparation can make all the difference in proper lifting. Before you grab the object in front of you, adopt a wide, crouched stance. Make sure your feet rest firmly on the floor and that your back is straight, not hunched. Stand slowly, avoid twisting to the side, and concentrate on pushing with your legs, rather than pulling with your back.If you struggle with back pain, experts will tell you to use proper lifting for any object below waist height—even a dropped pencil.Source of Information : Oreilly - Your Body Missing Manual

Friday, July 9, 2010

It’s often said that the rear end is the most heavily used part of the human body. If you’re an average person living in the modern world, you spend a lot of time pressing your behind into soft, yielding pieces of furniture. In fact, you probably spend more time sitting down (whether it’s working, eating, driving, watching television, or reading fine books like this one) than you spend in virtually any other position.With all our experience sitting, it’s a bit disappointing to learn that most of us aren’t very good at it. Proper sitting is surprisingly hard work, especially when you add computers, telephones, and office work into the mix. Part of the problem is that sitting “at the ready” quickly becomes tiring, and good posture requires constant vigilance. One funny Web video later, and you’ll be slouching into your computer screen.The first piece of advice for long-term sitters is to take frequent breaks. (You can find some simple stretches and exercises you can do without leaving your desk at http://backandneck.about.com/od/exercise/ig/Stretch-at-Your- Desk.) The second piece of advice is to conduct regular “posture checks.” With each posture check, your goal is to review what you’re doing and pull your body back into line. The most common mistakes include pushing out your stomach (which curves and overextends your back), hunching your shoulders, and craning your neck. To make sure you’re sitting pretty, use the picture on this page as a quick posture checklist.Source of Information : Oreilly - Your Body Missing Manual

Thursday, July 8, 2010

Standing is a seemingly simple activity that the human body doesn’t do very well. Our bodies are designed to handle much more ambitious activities (climbing hills, hunting elk, and so on). Keep us stuck in one place, and we suffer—our backs ache, our posture slips, and we end up with more spinal distress than a performer in Cirque du Soleil.

During short periods of standing, you can reduce strain by avoiding the worst mistakes. Keep your head, shoulders, and feet lined up (imagine a straight line that links the top of your head to the middle of your feet). The biggest backaches start when you pull your head forward or lean your upper body backward.

If you must stand for a long time, shift your weight from one foot to the other or rock your feet from heel to toe. Putting one foot on a very low rail, like the sort you find at some bars, can also reduce the pressure on your back. Posture experts say leaning is acceptable, but only if you put your lower back, shoulders, and the back of your head against a wall—a position that might draw a few curious stares.Source of Information : Oreilly - Your Body Missing Manual

Wednesday, July 7, 2010

Your back puts up with a great many indignities. Ordinarily, your spine adopts three natural curves that help distribute your body’s weight. They go by the names cervical, thoracic, and lumbar curves.

No matter how good your posture, when you stay in a single position for a long time (for example, when you stand in line, sit at a desk, or drive across the country), you put increased pressure on parts of your spine, and you usually end up flattening or excessively curving these parts of your back. Your muscles strain to compensate, causing problems that range from a stiff neck to an aching lower back.

There’s no ironclad defense against back problems. However, you can do a lot by observing good posture, practicing backstrengthening exercises, and avoiding back-straining experiences.

The first rule of good posture is to vary your position. Contrary to what you might think, good posture doesn’t involve locking your back into an ideal arrangement for hours at a time. In fact, the human back hasn’t quite caught up to the strains and stresses of modern-day activities like sitting in motor vehicles and doing office work. You’ll spare your spine a lot of pain by interrupting long, tedious activities (driving, typing, and so on) to take a quick stretch and have a walk around. If you can, limit yourself to 20 minutes of focused office work or an hour of uninterrupted driving before you take a quick refresher.

Tuesday, July 6, 2010

Of all the bones in your body, few are as important as the stack of 33 that forms your spine.

Your spine (or vertebral column, as it’s known to biologists and Trivial Pursuit players) is the centerpiece of your skeletal system—your body’s equivalent of the center pole in a circus tent. It anchors your body, allowing you to stand upright, support your head and arms, and keep your balance. It’s a central attachment point for countless muscles, and it encases your critically important spinal cord, which ferries commands from your brain to the far regions of your body (and sends sensory information in the reverse direction, from your body parts back to your brain).

Your spine is also one of the easiest parts of your body to injure—poor posture, repetitive actions, or heavy lifting can easily drive you to the medicine cabinet or leave you lying helplessly under an office table. In fact, back pain affects 80 percent of adults at some point, and nearly half of them suffer at least one bout of back pain every year. In the U.S., lower-back pain is the fifth most common reason for doctor visits.

Part of the reason your spine is so vulnerable is its complexity. Of its 33 bones, 24 are bony disks called vertebrae. Every two vertebrae form a separate joint, each with its own ligaments holding it together and its own tendons binding it to the appropriate muscles. This design lets you freely bend and twist your spine. Your body limits your range of motion not with the ligaments themselves, but with the bony protrusions of each vertebra, which lock together if you try to bend them past a certain point. This important safeguard prevents a strained back from causing life-threatening paralysis.

Between each pair of vertebrae is a spongy disk of cartilage. These disks become temporarily more compressed throughout the day, and permanently more compressed as you age. They’re the reason you go to bed a little bit shorter than when you woke up, and why you’re likely to lose an inch of height by the time you reach old age. They’re also the source of more serious, long-term back ailments. For example, the infamous “slipped disk” occurs when you inadvertently crush a piece of cartilage out of shape, making it bulge into a nearby nerve.

Monday, July 5, 2010

Arthritis is a group of conditions that cause joint problems, and they becomes increasingly common in the later stages of life. In the most common type of arthritis, osteoarthritis, the joint cartilage gradually wears away, allowing the bones to grind against each other. The causes aren’t clear, but heredity, excessive weight, old age, lack of physical exercise, and injury all seem to play a part. If you have joint pain or stiffness that lasts for more than two weeks, it’s best to check it out with your doctor.

Although doctors can’t cure osteoarthritis, you may be able to avoid it—or at least delay its onset. The best advice is to adopt a regular routine of strength exercises. You should also avoid straining your joints with repetitive motions or dramatic changes in the way you use them. (For example, don’t expect your body to make the jump from weekday office worker to long-weekend football superhero.)

Sunday, July 4, 2010

On their own, bones are a remarkable piece of biological machinery. But the true miracle just might be the way a skeleton that’s stronger than concrete still allows the supple movements of a ballet dance.

Joints are the means by which one bone glides, rotates, or bends around another. They ensure that your bones fit snugly together while allowing them an impressive range of movement. Different joints allow different types of movement—for example, joint limitations explain why you can’t spin your hand around your wrist or fold your head back until your ears rest on your shoulder blades. The image here shows four different joints, from the relatively simple folding joints at the knees and elbows to the more versatile ball-and-socket joints in your shoulders and hips.

Joints are a surprisingly complex part of your skeleton. The bones in a joint are padded with cartilage, braced with ligaments, and lubricated with a special fluid. Here’s how each part works:

• Cartilage. This tough, flexible tissue pads the end of the two bones that meet in a joint. Cartilage helps cushion and protect the joint, absorbing shocks and preventing friction. (Cartilage also supports other structures in your body—for example, it creates the shape of your ears and the tip of your nose.)

• Ligaments. Ligaments are sturdy bands of elastic tissue that connect one bone to another. Your body often uses them to support a joint— for example, four major ligaments hold your knee in place and connect it to your leg bones.

• Synovial fluid. This thick, stringy fluid fills many of your joints. It reduces friction between pieces of cartilage and other tissue in the joint, which helps reduce wear and tear.

Incidentally, “double-jointed” people don’t have extra joints, just abnormally expanded joint movement for some other reason. They may have misaligned joints, for example, or abnormally shaped bones, or weaker ligaments and tendons. Alternatively, they may be less sensitive to the signals that indicate when the bones of a joint are out of place. Whatever the case, their condition puts them at higher risk of bone injury and arthritis.

Synovial fluid is probably also responsible for the exquisitely annoying sound of knuckle cracking. The thinking is that over time, bubbles of gas accumulate in the synovial fluid of your joints. When you pull your finger ever-so-slightly out of place, the knuckle’s bones separate, and the tiny bubbles combine and burst in a distinctive pop. In theory, this practice could eventually cause loss of grip strength or joint pain, but so far no study has found knuckle cracking to cause anything more dangerous than a seriously annoyed spouse.

Saturday, July 3, 2010

A century ago Ebenezer Howard’s Garden Cities of To-morrow proposed a model for lowdensity, sustainable urban growth. A forerunner of today’s green movement, Howard envisioned networked towns as an alternative to an industrial world filling with high-rise cities. Ten towns with tens of thousands of people, he suggested, could have the same functional and administrative capacity of a single megacity.

The ancient Xinguanos built such a system, a flat, green style of urbanism or proto-urbanism: an inchoate garden city. Perhaps Percy Fawcett was in the right place but looking for the wrong thing: stone cities. What the small-scale centers lacked in size and elaborate structures, they made up for in numbers and integration. Had Howard known of them, he might have devoted a passage to the “Garden Cities of Yesterday.” The common conception of the city as a dense grid of masonry buildings dates to early desert oasis civilizations such as Mesopotamia but was uncharacteristic of many other environments. Not only the Amazon’s tropical forests but also temperate forest landscapes throughout much of medieval Europe were dotted with towns and villages of similar size to those in the Xingu.

These insights are especially important today as the southern Amazon is redeveloped, this time by Western civilization. The transitional forest of the southern Amazon is being quickly converted into farmland and pasture. At the present rate, it will be reduced to 20 percent of its original size over the next decade. Much of what is left will be restricted to reserves, such as the Xingu, where indigenous people are the stewards of the remaining biodiversity. In these areas, saving tropical forests and protecting indigenous cultural heritage are, in many respects, one and the same thing.

Friday, July 2, 2010

“Palatial” is not the word that usually comes to mind to describe a pole-and-thatch house. Most Westerners think “hut.” But the house that the Kuikuro were building for the chief when I arrived in 1993 was massive: well over 1,000 square meters. It is hard to imagine that a house built like a giant, overturned basket without stone, mortar or nails could get any bigger. Even the average Xinguano house, at 250 square meters, is as big as the average American home.

What makes the chief’s house stand out is not just size but also its position, located on the southern point of the central circular plaza. As one enters the village along the formal entry road, high-ranking families live to the right (south) and left (north). The arrangement reproduces, on a larger scale, the layout of an individual house, whose highest-ranking occupant hangs his hammock to the right, along the long axis of the house. The entry road runs approximately east-west; in the chief’s house, his hammock is oriented in the same direction. When a chief dies, he is also laid to rest in a hammock with his head to the west.

This basic corporeal calculus applies on all scales, from houses to the entire Upper Xingu basin. Ancient towns are distributed across the region and interconnected by a lattice of precisely aligned roads. When I first arrived in the area, it took weeks to map the ditches, plazas and roads using standard archaeological techniques. Beginning in 2002, we began using precise GPS, enabling us to map major earthworks in a matter of days. What we have found is an impressive degree of regional integration. The landscape planning seems almost overdetermined, with a specific place for everything. Yet it was based on the same basic principles of the current village. Main roads run east-west, secondary roads radiate out to the north and south, and smaller roads proliferate in other directions.

We mapped two hierarchical clusters of towns and villages in our study area. Each consists of a major ceremonial center and several large satellite towns in precise orientations relative to the center. These towns likely held 1,000 or more inhabitants. Smaller villages are located farther from the center. The northern cluster is centered on X13, which is not a town so much as a ritual center, rather like a fairground. Two large walled settlements lie equidistant to the north and south of X13, and two medium-size walled towns lie equidistant to the northeast and southwest. The southern cluster is slightly different. It is centered on X11, which is both a ritual center and a town, around which are medium- and small-size plaza settlements.

In land area, each cluster was more than 250 square kilometers, of which about a fifth was the built-up core area, making it roughly equivalent in size to a small modern city. Today most of the ancient landscape is overgrown, but forests in the core areas have distinctive concentrations of certain plants, animals, soils and archaeological artifacts, such as prolific ceramics. Land use was more intensive in the past, but the remains suggest that many practices were similar to those of the Kuikuro: manioc plots, small orchards of pequi fruit trees and fields of sapé grass, the preferred material for house thatch. The countryside was a patchy landscape interspersed with secondary forests that invaded fallow agricultural areas. Wetlands, which today are choked with Buriti palm, the most important industrial crop, preserve diverse evidence of fish farming, such as artificial ponds, raised causeways and weir footings. Outside the core areas was a more lightly populated green belt and even deeper forest wilderness between clusters. This forest, too, had its uses for animals, medicinal plants and certain trees, and it was considered the home of diverse forest spirits.

The areas in and around residential sites are marked by dark earth, which the Kuikuro call egepe, a highly fertile soil that has been enriched by household refuse and specialized soil-management activities, such as controlled burning of vegetation cover. People have altered soils the world over, making them darker, more loamy and richer in certain chemicals. In the Amazon these changes are particularly important for agriculture in many areas because the natural soil is so poor. In the Xingu, the dark earth is lessprevalent than some areas, because local populations depend mostly on manioc and orchards, which do not require high-fertility soils.

Identification of large walled settlements over an area about the size of Vermont suggests that at least 15 clusters were spread across the Upper Xingu. But most of the region is unstudied, so the true number could have been much higher. Radiocarbon dating of our excavated sites suggests that ancestors of the Xinguanos settled the area, most likely from the west, and began to mold the forests and wetlands to their design about 1,500 years ago or before. In the centuries before Europeans first discovered the Americas, the communities were re-formed into hierarchical clusters. Records date back only to 1884, so the settlement patterns are our only way of estimating the pre-Columbian population; the scale of the clusters suggests a regional population many times larger than today, perhaps numbering 30,000 to 50,000.

Thursday, July 1, 2010

When I ventured to Brazil in the early 1990s to study the deep history of the Xingu, lost cities were the furthest things from my mind. I had read Steinen but had barely heard of Fawcett. Although much of the vast Amazon basin was archaeological terra incognito, it was unlikely that ethnographers, much less local Xinguanos, had missed a large monolithic center towering over the tropical forests.

Nevertheless, signs of something more elaborate than present-day settlements were all around. Robert Carneiro of the American Museum of Natural History in New York City, who lived with the Kuikuro in the 1950s, had suggested that their settled way of life and productive agricultural and fi shing economy could support communities 1,000 to 2,000 strong—several times the contemporary population of a few hundred. He also cited evidence that indeed it once had: a prehistoric site (designated “X11” in our archaeological survey) that was surrounded by extensive ditches. The Villas Boas brothers— Brazilian indigenistas who were nominated for a Nobel Peace Prize for their part in creating the Xingu park—had reported such earthworks near many villages.

In January 1993, soon after I arrived in the Kuikuro village, the principal hereditary chief, Afukaka, took me to one of the ditches at a site (X6) they call Nokugu, named for the jaguar spirit being thought to live there. We passed local men who were raising a huge fish weir across the Angahuku River, which was already swelling from the seasonal rains. The ditch, which runs over two kilometers, was two to three meters deep and more than 10 meters wide. Even though I had expected to fi nd an archaeological landscape different from today’s, the scale of these ancient communities and their constructions surprised me. Kuikuro research assistants and I spent the following months mapping it and other earthworks at the 45-hectare site. Since that time, our team has studied numerous other sites in the area, hacking more than 30 kilometers of line-of-sight transects through the forest to map, examine and excavate the sites. Many Kuikuro helped in one way or another, and some became well versed in archaeology.

At the end of 1993, Afukaka and I went back to Nokugu so I could tell him what I had learned. We followed the contour of the site’s outer ditch and stopped at an earthen bridge, where a major road we had uncovered passed over it. I pointed down the arrow-straight ancient dirt road, which was 10 to 20 meters wide and led to another ancient site, Heulugihïtï (X13), about five kilometers away. We crossed the bridge and entered Nokugu.

The road, defined by low earthen curbs, widened to 40 meters—the size of a modern four-lane highway. After a couple of hundred meters, we passed over the inner ditch and stopped to look at our recently finished excavation trench, where we had found a funnel-shaped footing for a tree-trunk palisade. Afukaka told me a story of palisaded villages and raids in his people’s distant past.

As we moved farther into the ancient town, we passed through patches of forest, scrub and open areas that now cover the site—the footprints of diverse past activities. We emerged into a grassy glade of towering palms marking the former plaza. I slowly spun and pointed along the perfectly circular edge of the plaza, marked by a meter-high mound. The tall palms, I told him, had colonized the plaza centuries ago from compost gardens in domestic areas.

Leaving the plaza to explore the surrounding neighborhoods, we came across large refuse middens that closely resembled the one behind Afukaka’s own house. They were fi lled with broken pots that he noted were exactly like those his wives used to process and cook manioc, down to minute details. On a later visit, when we were excavating a pre Columbian house, the chief bent down in the central kitchen area, popped out a big hunk of pottery, and corroborated my sense that the daily life of the ancient society was much like today’s. “You’re right!” Afukaka exclaimed. “Look here, a pot support”— an undagi, as the Kuikuro call it, used to cook manioc.

These connections are what make the Xinguano sites so fascinating. They are among the few pre-Columbian settlements in the Amazon where archaeological evidence can be linked directly to present-day customs. Elsewhere, the indigenous culture was completely wiped out, or the archaeological record is spotty. The ancient orienwalled town I showed Afukaka was much like his current village, with its central plaza and radial roads, only it was 10 times larger.

Xingu HistoryRadiocarbon dating indicates that people have lived in the upper Xingu for at least 1,500 years.

6th century. The ancestors of today’s inhabitants moved in from the west.

13th century. Groups organized themselves into integrated clusters with a regional population estimated at 30,000 to 50,000.

1542. Spanish conquistador Francisco de Orellana led the fi rst European expedition down the Amazon, as chronicled by Gaspar de Carvajal.

18th century. Slave raids further decimated the Xinguano people.

1884. German anthropologist Karl von den Steinen visited the Xingu and estimated a population of 3,500.

1950s. Orlando, Cláudio and Leonardo Villas Boas led a campaign to found the Xingu reserve. The Xinguano population was about 500.

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In its broadest sense, science (from the Latin scientia, meaning "knowledge") refers to any systematic knowledge or practice. In its more usual restricted sense, science refers to a system of acquiring knowledge based on scientific method, as well as to the organized body of knowledge gained through such research.

Fields of science are commonly classified along two major lines: natural sciences, which study natural phenomena (including biological life), and social sciences, which study human behavior and societies. These groupings are empirical sciences, which means the knowledge must be based on observable phenomena and capable of being experimented for its validity by other researchers working under the same conditions.